1. Field of the Invention
The invention pertains to pulse radar receiver systems and more particularly to means for significant improvement of signal detection in pulse radar receivers exposed to clutter interference signals which may be of relatively high magnitude compared to desired target echoes, clutter signals such as rain, ground, and sea clutter return signals.
2. Description of the Prior Art
In prior art radar systems, various arrangements have been proposed for improving signal detectability, especially in the presence of interfering clutter signals such as ground return or rain return clutter. Moving target discriminating systems have, for instance, afforded a degree of signal-to-interference ratio improvement in efficiently diminishing the effects of clutter signals caused by stationary reflectors, such as the earth's surface. Non-adaptive radar signal processors provide acceptable clutter rejection for particular ranges and for particular types of clutter, but the performance of such systems degrades under varying clutter conditions. Further, when no interfering clutter is present, conventional non-adaptive processors are not generally optimum in the presence of ordinary electrical noise alone.
Matched filter signal processors have also been of interest for diminishing the effects of interfering clutter. However, such devices have not proven to achieve useful results under dynamically changing clutter conditions and in all range sectors. Defective results are noted particularly in matched filter operation upon the echo returns from multiple-pulse burst transmission radar systems. Matched filter processors fail to give required signal interference cancellation, for example, when the target of interest lies in particular periods of the several interpulse periods of the multi-pulse burst. Only in other particular interpulse periods may an acceptable signal-to-interference ratio be achieved. Thus, the total effect in such matched filter systems of the ultimate addition of the individual returns from a multiple-pulse burst is to yield an output having a degraded signal-to-interference ratio.